৪৯তম বিসিএস ⎯ প্রাণ রসায়ন [৬০১]

Explanation: Disaccharides are carbohydrates made up of two monosaccharides. Lactose is composed of one glucose molecule and one galactose molecule. Glucose, fructose, and galactose are all monosaccharides.

Explanation: Carbohydrates are the body's preferred and most readily available source of energy. They are broken down into glucose, which is used by cells for fuel. Proteins are primarily for building tissues, and fats are for long-term energy storage and insulation.

Explanation: The approximate energy values are: carbohydrates, 4 kcal/g; proteins, 4 kcal/g; and fats, 9 kcal/g.

Explanation: Monounsaturated fats, found in foods like avocados and olive oil, are considered beneficial for heart health as they can help lower LDL ("bad") cholesterol levels. Saturated and trans fats are generally considered unhealthy.

Explanation: SDA, also known as the thermic effect of food (TEF), is the metabolic increase that occurs after eating. It represents the energy cost of processing food for use and storage.

Explanation: The RQ is the ratio of carbon dioxide produced to oxygen consumed, which indicates which macronutrient is being metabolized for energy.

Explanation: The RQ for carbohydrates is 1.0, because the amount of CO₂​ produced is equal to the amount of O₂​ consumed during their oxidation.

Explanation: While protein can be used for energy, fats are the main form of long-term energy storage.

Explanation: Complete proteins contain all nine essential amino acids. Quinoa is one of the few plant-based sources that is a complete protein.

Explanation: A negative nitrogen balance occurs when the body excretes more nitrogen than it consumes, indicating a net loss of body protein.

Explanation: A calorimeter, specifically a bomb calorimeter, is used to measure the heat produced when a food sample is burned, which determines its energy content.

Explanation: Foods can be classified based on their source, with major categories being plant-based and animal-based.

Explanation: Body fat serves as insulation to maintain body temperature and cushions vital organs.

Explanation: The RQ for fats is typically around 0.7, as the complete oxidation of fats requires more oxygen relative to the amount of CO₂​ produced.

Explanation: The SDA for protein is the highest, at approximately 20-30% of its caloric value, due to the complex metabolic processes required to break it down.

Answer: b) Increased folic acid and iron intake
Explanation: During pregnancy, particularly in the 2nd trimester, demand for folic acid (to prevent neural tube defects) and iron (to support maternal blood volume and fetal growth) is significantly increased. Carbohydrates and proteins are also important, but iron and folic acid are critical.

Answer: b) 500 kcal/day
Explanation: Lactation increases energy requirements due to milk production. On average, an additional 500 kcal/day is recommended to maintain maternal health and support adequate breast milk production.

Answer: c) Vitamin A
Explanation: Vitamin A deficiency is prevalent in Bangladesh and leads to xerophthalmia and night blindness, especially in children. The government runs Vitamin A supplementation programs to combat this.

Answer: c) Growing child
Explanation: Children in the growth phase need the highest protein per kg body weight to support tissue synthesis and growth. While pregnancy and lactation increase protein needs in absolute terms, per body weight basis, growing children require more.

Answer: c) Stunting
Explanation: According to recent Bangladesh Demographic and Health Surveys (BDHS), stunting (low height-for-age) is the most prevalent form of malnutrition, affecting ~28% of children under 5. Kwashiorkor and marasmus are less common but severe.

Answer: b) Niacin (B3)
Explanation: Pellagra occurs due to niacin deficiency. In regions where maize is the staple without proper processing, niacin deficiency may occur. Historically observed in poorer populations with limited dietary diversity.

Answer: b) Double burden of malnutrition (undernutrition and obesity) is emerging
Explanation: Bangladesh faces a double burden of malnutrition: undernutrition (stunting, wasting, micronutrient deficiencies like Vitamin A, iron, iodine) and rising overweight/obesity in urban populations due to lifestyle changes.

Answer: a) Water-soluble and fat-soluble
Explanation: Vitamins are divided into fat-soluble (A, D, E, K) and water-soluble (B-complex, C) based on solubility, absorption, and storage characteristics.

Answer: d) Vitamin C
Explanation: Vitamin C is water-soluble, while A, D, E, and K are fat-soluble and stored in liver/adipose tissue.

Answer: a) β-carotene
Explanation: Plant-derived β-carotene is converted into retinal in the body and then to retinol (active Vitamin A).

Answer: b) xerophthalmia
Explanation: Vitamin A is essential for the formation of rhodopsin in the retina; deficiency causes nyctalopia (night blindness).

Answer: b) Sunlight exposure
Explanation: UV radiation converts 7-dehydrocholesterol in the skin into Vitamin D3 (cholecalciferol). Food sources are minor contributors.

Answer: b) Rickets
Explanation: Vitamin D is essential for calcium and phosphate absorption; deficiency in children causes rickets (bone deformities). In adults, it causes osteomalacia.

Answer: b) Hemorrhage due to clotting defect
Explanation: Vitamin K is needed for γ-carboxylation of clotting factors (II, VII, IX, X). Deficiency leads to impaired coagulation.

Answer: b) Beriberi
Explanation: Thiamine deficiency causes dry and wet beriberi and Wernicke-Korsakoff syndrome, due to impaired carbohydrate metabolism.

Answer: b) Megaloblastic anemia with neurological symptoms
Explanation: B12 deficiency impairs DNA synthesis, leading to megaloblastic anemia, and also affects myelin synthesis causing neuropathy.

Answer: b) Vitamin B1 (Thiamine)
Explanation: Chronic alcoholics are prone to thiamine deficiency due to poor diet and impaired absorption → Wernicke-Korsakoff syndrome.

Answer: b) Biotin (B7)
Explanation: Biotin acts as a coenzyme in carboxylase enzymes, e.g., pyruvate carboxylase, acetyl-CoA carboxylase.

Answer: a) FMN and FAD
Explanation: Riboflavin (B2) is converted into flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD), which are electron carriers in redox reactions.

Answer: c) B6
Explanation: Vitamin B6 (pyridoxine) is converted to PLP, a coenzyme in amino acid metabolism (transamination, decarboxylation).

Answer: b) Megaloblastic anemia
Explanation: Folate is required for DNA synthesis. Deficiency results in megaloblastic anemia (enlarged immature RBCs).

Answer: b) Methyl group transfer
Explanation: Vitamin B12 is required for methionine synthase (methylation of homocysteine to methionine) and methylmalonyl-CoA mutase.

Answer: a) Vitamin B9 (Folate)
Explanation: Folate deficiency during early pregnancy increases the risk of neural tube defects (spina bifida, anencephaly).

Answer: c) 75–90 mg/day
Explanation: RDA of Vitamin C is 75 mg/day for women and 90 mg/day for men, higher in smokers due to oxidative stress.

Answer: b) Calcium
Explanation: About 99% of body calcium is stored in bones and teeth. It plays key roles in bone structure, blood clotting, nerve transmission, and muscle contraction.

Answer: c) Anemia
Explanation: Iron is a critical component of hemoglobin. Deficiency causes microcytic hypochromic anemia (pale, small RBCs).

Answer: c) 1000 mg/day
Explanation: Recommended dietary allowance (RDA) for adults is ~1000 mg/day. Higher needs exist in adolescents, pregnancy, and lactation.

Answer: c) Red meat and liver
Explanation: Heme iron from animal sources (meat, liver) is absorbed more efficiently (~20–30%) than non-heme iron from plants (~5–10%).

Answer: b) Growth retardation and delayed wound healing
Explanation: Zinc is essential for DNA/RNA synthesis and cell division. Deficiency causes growth delay, immune dysfunction, and skin lesions.

Answer: c) Glutathione peroxidase
Explanation: Selenium is a cofactor for glutathione peroxidase, which protects cells from oxidative damage by reducing hydrogen peroxide.

Answer: b) Menkes disease and anemia
Explanation: Copper is needed for enzymes like cytochrome oxidase and ceruloplasmin. Deficiency causes hypochromic anemia, bone abnormalities, and Menkes kinky hair disease.

Answer: b) Chromium
Explanation: Chromium potentiates insulin action by enhancing glucose uptake. Deficiency may lead to impaired glucose tolerance.

Answer: b) Bone mineralization and prevention of dental caries
Explanation: Fluoride strengthens teeth enamel and bones. Deficiency increases dental caries, while excess causes fluorosis.

Answer: b) ATP metabolism and enzyme activation
Explanation: Magnesium stabilizes ATP and acts as a cofactor for over 300 enzymes, particularly those involving phosphorylation.